Balloon catheter with stent securement means

ABSTRACT

An assembly for delivery and deployment of an inflation expandable stent within a vessel is comprised of a catheter, and inflation expandable stent, an expandable balloon, and a securement means such as a corrugated tube component or an expandable tube component. The tube component is mounted on the inner shaft beneath the balloon and provides increased securement to the stent in a reduced delivery diameter to maintain the stent on the catheter during delivery to the deployment site. The tube component is adhered to the inner shaft and has a plurality of ribs or is fluid expandable to no more than the delivery diameter, and may be comprised of more than one separately inflatable pouch expandable to provide the stent with a substrate seat with increased friction and to decrease the slack in stent recoil crimping. The assembly is used in a method for delivering and deploying a stent, and also adds safety when loading/crimping the stent onto a balloon.

REFERENCES TO CO-PENDING APPLICATIONS

This application is a continuation-in-part of application Ser. No.08/697,453 filed Aug. 23, 1996 now abandoned entitled PRE-MOUNTED STENTDELIVERY DEVICE WITH INFLATABLE TUBE COMPONENT, herein incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an assembly method for delivering anddeploying an inflation expandable stent, particularly within a lumen ofa body vessel. More specifically, this invention relates to theprovision of a securement component positioned over the inner catheter,and beneath a balloon and a loaded stent, to maintain the stent on thecatheter assembly during delivery to a stent deployment site.

2. Description of Relevant Art

Stents and stent delivery assemblies are utilized in a number of medicalprocedures and situations, and as such their structure and function arewell-known. A stent is a general cylindrical prosthesis introduced via acatheter into a lumen of a body vessel in a configuration having agenerally reduced diameter and then expanded to the diameter of thevessel. In its expanded configuration, the stent supports and reinforcesthe vessel walls while maintaining the vessel in an open, unobstructedcondition.

Both self-expanding and inflation expandable stents are well-known andwidely available. Self-expanding stents must be maintained underpositive external pressure in order to maintain their reduced diameterconfiguration during delivery of the stent to its deployment site.Inflation expandable stents (also known as balloon expandable stents)are crimped to their reduced diameter about the delivery catheter,positioned at the deployment site, and then expanded to the vessel bydiameter by fluid inflation of the balloon positioned between the stentand the delivery catheter. The present invention is particularlyconcerned with enhanced stent securement and safer stent loading in thedelivery and deployment of balloon expandable stents.

In angioplasty procedure, there may be restenosis of the artery, whicheither necessitates another angioplasty procedure, a surgical bi-passprocedure, or some method of repairing or strengthening the area. Toprevent restenosis and strengthen the area, a physician can implant anintravascular prosthesis for maintaining vascular patency, i.e. a stent,inside the artery at the lesion. The stent is expanded to a largerdiameter for placement in the vasculature, often by the balloon portionof the catheter. Stents delivered to a restricted coronary artery,expanded to a larger diameter as by a balloon catheter, and left inplace in the artery at the site of a dilated lesion are shown in U.S.Pat. No. 4,740,207 to Kreamer; U.S. Pat. No. 5,007,926 to Derbyshire;U.S. Pat. No. 4,733,665 to Palmaz; U.S. Pat. No. 5,026,377 to Burton etal.; U.S. Pat. No. 5,158,548 to Lau et al.; U.S. Pat. No. 5,242,399 toLau et al.; U.S. Pat. No. 5,344,426 to Lau et al.; U.S. Pat. No.5,415,664 to Pinchuck; U.S. Pat. No. 5,453,090 to Martinez et al.; U.S.Pat. No. 4,950,227 to Savin; U.S. Pat. No. 5,403,341 to Solar; U.S. Pat.No. 5,108,416 to Ryan et al.; and European Patent Application No.707837A1 to Scheiban, all of which are incorporated herein by reference.A stent particularly preferred for use with this invention is describedin PCT Application No. 96/03092-A1, published Feb. 8, 1996, the contentof which is incorporated herein by reference.

In advancing a balloon expandable stent through a body vessel to thedeployment site, there are a number of important considerations. Thestent must be able to securely maintain its axial position on thedelivery catheter. The stent, particularly its distal and proximal ends,are sometimes protected to prevent distortion of the stent, and minimizetrauma to the vessel walls. Balloon expandable stent delivery anddeployment assemblies are known which utilize restraining means thatoverlay the stent during delivery. U.S. Pat. No. 4,950,227 to Savin etal., relates to a balloon expandable stent delivery system in which asleeve overlaps the distal or proximal margin (or both) of the stentduring delivery. During inflation of the stent at the deployment site,the stent margins are freed of the protective sleeve(s) and the sleevesthen collapse toward the delivery catheter for removal. A number ofballoon expandable stent delivery and deployment assemblies do not useoverlaying restraining members, such as the Savin sleeves, to positionthe stent for delivery. European Patent Application No. EP 055 3960A1 toLau et al., uses an elastic sheath interspaced between the balloon andthe stent. The sheath is said to act as a barrier to protect the balloonfrom the stent, allow uniform stent expansion, decrease balloondeflation time, prevent undesirable balloon flattening upon deflationand provide a friction substrate for the stent. The Lau sheath can bepositioned on the inside or outside of the balloon. U.S. Pat. No.5,409,495 to Osborne, similarly uses an elastic sleeve or sheathsurrounding and in contact with the balloon for controlling the balloonradial expansion. In addition, Osborne is said to use restraining bandsor a pair of balloons to achieve controllable stent expansioncharacteristics. U.S. Pat. No. 5,403,341 to Solar, relates to stentdelivery and deployment assembly which uses a retaining sheathpositioned about opposite ends of the compressed state. The retainingsheaths of Solar are adapted to tear under pressure as the stent isradially expanded, thus releasing the stent for engagement with thesheaths. U.S. Pat. No. 5,108,416 to Ryan et al. describes a stentintroducer system which uses one or two flexible end caps and annularsocket surrounding the balloon to position the stent during introductionto the deployment site. The content of all of these patents isincorporated herein by reference.

In positioning a balloon expandable stent on the delivery catheter overthe fluid expandable balloon, the stent must be smoothly and evenlycrimped to closely conform to the overall profile of the catheter andthe unexpanded balloon. It has been noted that, due to physicalproperties of the material used in manufacturing the stent (stainlesssteel, tantalum, platinum or platinum alloys, or shape memory alloyssuch as Nitinol™) there is a certain amount of "recoil" of the stentdespite the most careful and firm crimping. That is the stent evidencesa tendency to slightly open up from the fully crimped position and oncethe crimping force has been released. For example, in the typical stentdelivery and deployment assembly, if the stent has been fully crimped toa diameter of approximately 0.0035", the stent has been observed to openup or recoil to approximately 0.0037". This phenomenon has beencharacterized as "recoil crimping". Due to recoil crimping to thisslightly enlarged diameter, it can be understood that the stent tends toevidence a certain amount of looseness from its desired close adherenceto the overall profile of the underlying catheter and balloon. That is,the stent tends to have a perceptible relatively slack fit in itsmounted and crimped position. During delivery, the stent can thus tendto slip and dislocate from its desired position on the catheter or evenbecome separate from the catheter, requiring further intervention by thephysician.

Further, there is a possibility of damaging the balloon during the stentcrimping as a result of pinching the balloon material between the metalstent and any metal (or protruding object) on the inner guide lumen(e.g. marker bands).

According to the present invention, a securement means such as acorrugated (accordion-type) tube is secured over the inner catheterbeneath the balloon to compensate for the undesired looseness or slackthat due to recoil crimping and to aid in securing the stent to theballoon, as well as protecting the balloon material from beingsandwiched between the stent and any metal or protruding item which maybe mounted on the inner shaft/guide wire lumen, for delivery of thestent. The corrugated tube provides additional volume for improved stentsecurement, i.e. more surface area to crimp onto, and also maintainsflexibility. In addition, when metal marker bands are employed on theinner catheter, the tubing aids in preventing damage to the balloonduring crimping/loading of the stent. The tubing, which may beinflatable, compensates for the perceptible looseness due to recoilcrimping and secures the stent during tracking and delivery and providesa good friction fit to the stent and insures good contact between thestent and underlying balloon and catheter, instead of merely relying onthe bulk of the flaccid balloon over the underlying catheter to hold thestent on. According to the present invention, the tubing component willcompensate for slackness in the fit of the stent due to recoil crimping.

According to another embodiment of the present invention, the securementmeans is an expandable tube component positioned under the expandableballoon to compensate for this undesired looseness or slack fit due torecoil crimping and to aid in securing the stent to the balloon and thecatheter for delivery. The expandable tube component and the expandableballoon are each provided with separate, individually controllable fluidinflation sources. Once the stent has been fully crimped to conform tothe overall profile of the catheter, the expandable balloon, and theunderlying expandable tube component, the tube component is inflated.The tube component is inflated to at least the limits of the elasticdeformation of the fully crimped stent. It is desirable to slightlyfurther inflate the tube component to a pressure at which the fullycrimped stent just begins to plastically deform. That is, the tubecomponent may be inflated to a point at which the stent is just barelybeginning to provide resistance to the expansion of the tube component,which is also characterized as a point at which the stent just barelybegins to expand beyond the crimped position (taking into considerationthe recoil crimping phenomenon). The desired pressure to which the tubecomponent is inflated is characterized as the "securement pressure". Theapplication of securement pressure to the tube component compensates forthe perceptible looseness due to recoil crimping and secures the stentduring tracking and delivery. The application of securement pressure tothe tube component provides a good friction fit to the stent and ensuresgood contact between the stent and the underlying balloon, "securementpressurized" tube component and catheter. The desired diameter of thestent upon the application of securement pressure to the tube componentis characterized as the "delivery diameter", because in this conditionthe stent can safely, reliably and securely be delivered to thepre-selected position within a body vessel. Instead of merely crimpingthe stent onto the balloon and the underlying catheter and relying onthe bulk of the flaccid balloon to hold the stent on, according to thepresent invention, the expandable tube component will compensate forslackness in the fit of the stent due to recoil crimping. Prior toinflation of the tube component to the securement pressure, thephysician preparing the assembly may manually sense a looseness of thestent in its position. When the tube component has been inflated to thenecessary securement pressure, the physician will manually sense thatthe stent is securely retained or "stuck" in position. The expandabletube component is designed and constructed to be expandable to no morethan is necessary to compensate for recoil crimping and is incapable ofoverexpanding to provide the pressure needed to fully expand the stentto its deployment position.

There are a number of descriptions of catheters which use a pair ofcoaxial, at least partially coextensive balloons. U.S. Pat. No.5,512,051 to Want et al., describes a slip layered balloon made of aplurality of layers with a low friction substance between the layers.During expansion the layers are able to slide relative to each othersoftening the balloon while maintaining its strength. U.S. Pat. No.5,447,497 to Sogard et al., relates to s a dual layered balloon, inwhich one balloon is compliant and the other is non-compliant, so thatthe balloon assembly has a non-linear compliance curve. U.S. Pat. No.5,358,487 to Miller, describes a balloon catheter having an outerballoon surrounding an inner balloon. The inner balloon has a maximuminflation diameter less than that of the outer balloon, so that, uponinflation, the inner balloon bursts at a certain diameter, allowing theouter balloon to be further expanded. U.S. Pat. No. 5,290,306 to Tottaet al., relates to a balloon catheter with an outer elastomeric sleeveto provide the balloon with pin hole and abrasion resistance. U.S. Pat.No. 5,049,132 to Shaffer et al., describes a first balloon and a secondballoon, each having separate inflation lumens, the second balloonhaving apertures for controlled administration of a medicationtherethrough. U.S. Pat. No. 4,608,984 and 4,338,942 to Fogarty, eachrelate to a catheter with an inner non-elastic balloon and an outerelastic balloon. In each patent, the outer balloon aids in collapse andretraction of the inner balloon. U.S. Pat. No. 4,328,056 to Snooks,describes a method of making a double cuffed endotracheal tubecomponent. However, none of these references show, suggest or renderobvious an inner balloon, in conjunction with an outer deploymentinflatable balloon, to provide securement pressure to a compressed stentduring delivery to a site within a body vessel.

The art referred to and/or described above is not intended to constitutean admission that any patent, publication or other information referredto herein is "prior art" with respect to this invention. In addition,this section should not be construed to mean that a search has been madeor that no other pertinent information as defined in 37 C.F.R. §1.56(a)exists.

SUMMARY OF THE INVENTION

The present invention is an assembly for delivery and deployment of aninflation expandable stent within a vessel. The assembly comprises acatheter, an expandable balloon mounted on the catheter, a stentsecurement means mounted on the catheter beneath or within the balloon,and a stent mounted on the balloon. The catheter has proximal and distalends. The stent is inflation expandable from a delivery diameter to adeployment diameter. The delivery diameter is reduced from thedeployment diameter for conforming the stent to the catheter. The stent,in its delivery diameter, is coaxially mounted on the catheter near thecatheter distal end. The expandable balloon is coaxially mounted on thecatheter axially within the stent. The balloon is designed and adaptedfor expansion of the stent from the delivery diameter to the deploymentdiameter upon application of fluid deployment pressure to the balloon.The securement means may be corrugated tubing mounted and adheredcoaxially onto the catheter and situated between the balloon and thecatheter itself. Alternatively, the securement means may be anexpandable tube component mounted on the catheter. The expandable tubecomponent is coaxially mounted on the catheter, axially within theexpandable balloon. The expandable tube component is designed andadapted for fluid expansion to provide a securement pressure to thestent in the delivery diameter to maintain the stent in position on thecatheter during delivery to the deployment site. The expandable tubecomponent is sized and constructed to be fluid expandable to no morethan the delivery diameter. The expandable tube component or corrugatedtube is essentially equal in length to the stent and the stent ispositioned on the assembly essentially coextensive with the tubecomponent. When the stent is crimped and loaded onto the balloon, theballoon is situated therefore between the stent and the securementmeans. The securement means is preferably essentially equal to thelength of the stent and the stent is positioned on the assemblyessentially co-extensive with the tube component. The present inventionis particularly directed to improved arrangements for releasablyattaching the stent to the catheter to facilitate delivery thereof.Generally, the stent is held in place upon the catheter by means of anenlarged body carried by the catheter shaft within the balloon to whichthe stent and the balloon are fitted, as by crimping. The securementmeans on the catheter effectively holds the stent in place, takes up theslack due to recoil and protects the balloon material from being damagedduring crimping.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a side profile section showing a balloon expandable stentdelivery and deployment assembly, with the stent crimped to deliverydiameter onto the balloon, the underlying corrugated tube component andthe catheter.

FIG. 2 is a side profile section, similar to FIG. 1, with the balloonand the stent fully inflated to deployment diameter.

FIG. 3 is a perspective view of the corrugated tubing of the presentinvention.

FIGS. 4-6 are side profile sections showing alternative embodiments ofballoon expandable stent delivery and deployment assemblies, having thetubing component formed in a plurality of sections.

FIGS. 7-8 are side profile sections showing alternative embodiments ofthe balloon expandable stent delivery and deployment assemblies, thetube component inflatable to add securement pressure.

FIG. 9 is a side profile section showing a balloon expandable stentdelivery and deployment assembly, with the stent crimped to deliverydiameter onto the balloon, the underlying tube component and thecatheter, and also having containment sleeves covering the ends of thestent.

FIG. 10 is a side profile section showing a balloon expandable stentdelivery and deployment assembly, with the stent crimped to deliverydiameter onto the balloon, the underlying tube component and thecatheter, and also having a pull-back wire attached to the tubecomponent.

FIG. 11 is a side profile section of an alternative embodiment showing aballoon expandable stent delivery and deployment assembly, with thestent crimped to delivery diameter onto the balloon, the underlyinginflating tube component and the catheter and with the inflating tubecomponent inflated to securement pressure.

FIG. 12 is a side profile section, similar to FIG. 11, with the balloonand the stent fully inflated to deployment diameter.

FIG. 13 is a side profile section showing an alternative embodiment of aballoon expandable stent delivery and deployment assembly, having a tubecomponent formed in several sections.

FIGS. 14, 15 and 16 are cross-sectional views taken along lines 4--4,5--5 and 6--6 of FIG. 13, respectively.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 illustrate a side profile section showing an inflationexpandable stent delivery and deployment assembly, generally designated10. Assembly 10 includes a catheter comprised of inner shaft 12 andouter shaft 13 of the coaxial type and an optional retractable deliveryshaft 11 (typically called a guide catheter, shown retracted in FIG. 2),an inflation expandable balloon 14, a corrugated/ribbed stent securementdevice 16, optional marker bands 17 and an inflation expandable stent18. Any conventional type of catheter may be used, such as a catheter ofthe type generally used for PTA or PTCA angioplasty procedures, forprostate therapy, and TTS endoscopic catheters for gastrointestinal use.However, coaxial types as show are most preferred. The particularcatheters 12 and 13 shown are formed of a biocompatible and hydrophiliccompatible material, such as a lubricous polyimide or poly ethylene.Other suitable materials for the catheters 12 and 13 include nylons,urethanes, and polypropylene materials compatible with coatings such assilicone and/or hydrophilic coatings. In addition to hydrophiliccompatible materials, any biocompatible material may be used. Forexample, polyethylene or polypropylene can be coated with a hydrophilicmaterial to render them hydrophilic compatible. Suitable catheters foruse according to the present invention include a number of cathetersavailable from SciMed Life Systems, Inc., Maple Grove, Minn., theassignee of the present invention, such as BANDIT™, COBRA™, VIVA™, VIVAPRIMO™, MAXXUM™, MAXXUM ENERGY™ and RANGER™ catheters.

Securement device 16 is fixed at its distal and/or proximal ends toinner shaft 12 at a position to be encompassed within the distal andproximal ends of the outer balloon 14. According to art-recognizedconvention, the length L-B of the balloon 14 is defined as the length ofthe body portion of the balloon 14, excluding the terminal cone sections20. As seen in FIG. 2, the body portion of the balloon 14 is generallycylindrical when in its deployed or inflated condition. Securementdevice/tube component 16 is illustrated as having terminal sections21,22. It is to be understood that, according to the present invention,either of the terminal sections 21, 22 may be relatively cone shaped,relatively vertical, relatively flat or of any other configuration knownto those of skill in this art. A preferred length L-T of the tubing 16is illustrated in FIGS. 1 and 2 as substantially equal to the length L-Bof balloon 14, and substantially equal to the length L-S of stent 18.However, according to the present invention, stent 18 should besupported by the underlying tube component 16 for a length sufficient topermit accomplishment of the stated purpose of the tube component 16, toprovide a superior securement and protective surface for stent 18 tomaintain stent 18 in position with assembly 10 and to protect theballoon material during loading/crimping. It is also within the presentinvention for the tube component 16 to be slightly shorter than stent18, for example, the distal end 19 of stent 18 may extend distallybeyond the distal end 22 of tube component 16 (not shown), so that thedistal end 19 of stent 18 can be crimped over the distal end 22 of tubecomponent 16 to prevent the distal end 19 of stent 18 from catching andtending to snag or further open as it is maneuvered within a bodyvessel. As has been explained above, tube component 16 is designed andconstructed to have enough flexibility and have enough volume to no morethan is necessary to compensate for recoil crimping of stent 18 and toclosely accommodate (or even slightly over stress) the delivery diameterof stent 18, taking into consideration the thickness of the interveninguninflated balloon 14. Typically, the tube component 16 will have aconsistent frequency of ribs, but may also vary by having intermittentgroups of ribs along the tubing.

The balloon and the crimped stent slightly conform to the undulations ofthe tube component for greater securement, but this conformation is notillustrated.

Tube component 16 may be formed from a thermoplastic material,preferably a low modulus polymer, such as Surlyn™, Pebax and urethane.The device such as polypropylene, low density polyethylene (LDPE), highdensity polyethylene (HDPE), ethylene vinyl acetate (EVA), nylon,polyester and polyethylene terephthalate ("PET"), may be preparedthrough free blowing in a mold or inside a coil. Tubing is extruded withrelatively thin walls and then free-blown in a mold, coil or otherfixture to form the ribs/corrugation.

A balloon 14 for use according to the present invention may be anyconventional balloon for catheter delivery, such as a balloon of thetype generally used for PTA and PTCA procedures. Typically, balloon 14is fixed at its distal end to inner shaft 12 near the catheter distalend and at its proximal end to inner shaft 12, near the distal end ofthe outer shaft 13. Balloon 14 is inflatable through an inflationconduit 23, i.e., the space between coaxial inner shaft 13 and outershaft 13 of the catheter. The distal and proximal ends of balloon 14 areshown in FIGS. 1 and 2 positioned exterior to the distal and proximalends of tube component 16, respectively, and of a length L-B generallyequal to the length L-T of the tube component 16. To be compatible withthe tube component 16 illustrated in FIGS. 1 and 2 and described above,balloon 14 is inflatable at deployment to about the diameter of the bodyvessel in which the stent 18 is to be deployed. Balloon 14 may be formedof a compliant or non-compliant material, such as polyethylene or anystandard balloon material. Compliant materials include low pressure,relatively soft or flexible polymeric materials, such as thermoplasticpolymers, thermoplastic elastomers, polyethylene (high density, lowdensity, intermediate density, linear low density), various co-polymersand blends of polyethylene, ionomers, polyesters, polyurethanes,polycarbonates, polyamides, poly-vinyl chloride,acrylonitrile-butadiene-styrene copolymers, polyether-polyestercopolymers, and polyetherpolyamide copolymers. Suitable materialsinclude a copolymer polyolefin material available from E.I. DuPont deNemours and Co. (Wilmington, Del.), under the trade name Surlyn™ Ionomerand a polyether block amide available under the trade name PEBAX™.Non-compliant materials include relatively rigid stiff high pressurepolymeric materials, such as thermoplastic polymers and thermosetpolymeric materials, poly(ethylene terephthalate) (commonly referred toas PET), polyimide, thermoplastic polyimide, polyamides, polyesters,polycarbonates, polyphenylene sulfides, polypropylene and rigidpolyurethanes, or combinations thereof. The balloon 14 typically has awall thickness of about 0.0007-0.004" for example.

A stent for use according to the present invention may be anyconventional type of balloon expandable stent, including stents of thetype used for PTA and PTCA angioplasty procedures, for prostate therapy,and TTS endoscopic catheters for gastrointestinal use. Suitable stentmaterial is biocompatible stainless steel in the form of sheet metal,tube component wire or Nitinol. A preferred stent is described in PCTApplication No. 960 3072 A1, published Feb. 8, 1996, the content ofwhich is incorporated herein by reference. All such stents arewell-known in this art generally and additional examples are describedin U.S. Pat. No. 5,507,768 to Lau et al.; in U.S. Pat. No. 5,458,615 toKlemm et al.; in U.S. Pat. No. 5,226,899 to Scheiban; in U.S. Pat. No.4,875,480 to Imbert; in U.S. Pat. No. 4,848343 to Wallsten et al.; andin U.S. Pat. No. 4,733,665 to Palmaz. Stent 18 as shown in FIGS. 1 and 2is positioned on balloon 14, which is over the underlying tube component16, at the distal end of the catheter. The length L-S of stent 18 isshown as essentially equal or slightly smaller than the length L-T oftube component 16 and is positioned on assembly 10 to be coextensivewith tube component 16. In this position, stent 18 is shown in FIG. 1crimped to its delivery diameter D1, which is about 0.035-0.45" forexample.

As discussed above, despite the most careful and firm crimping of stent18 to closely conform to the overall profile of the catheter unexpandedballoon 14 and underlying tube component 16, there is a certain amountof "recoil" of stent 18 or a tendency of stent 18 to slightly open froma desired hypothetical minimum crimped diameter. The actual minimumdiameter achievable for fully crimped stent 18 on assembly 10 isreferred to as stent 18 delivery diameter D1. This tendency of stent 18to open or recoil slightly when crimped on assembly 10 has beencharacterized as "recoil crimping". In FIG. 1, tube component 16 isshown at a diameter which is generally sufficient to compensate for anyslack or looseness between crimped stent 18 and the overall profile ofthe catheter, the unexpanded balloon 14 and the underlying tubecomponent 16 due to recoil crimping.

FIG. 2 illustrates a side profile section showing a stent delivery anddeployment assembly 10 of this invention with balloon 14 fluid inflatedto its fully expanded position. As a result of the fluid inflation ofthe balloon 14, stent 18 has also been fully expanded to its deploymentdiameter D2 in which it can be deployed against the walls of a bodyvessel in which it is situated.

FIG. 3 illustrates the preferred configuration of the tube component 16.The tube component has a plurality of ribs 30 and is configured in acorrugated or accordion fashion. The ends of the tube component 16, 22and 21, are substantially rib-free so as to provide a flat surface toreceive an adhesive and thereby bond to the inner shaft 12. Preferableadhesives include cyanocrylates such as Loctite 4061/4011 or urethanes,such as H. B. Fuller 3507/3506. The tube component may also be heatbonded to the inner shaft. The ribs may vary in frequency and spacing.

Tube component 16 may have different configurations in otherembodiments, as shown in FIGS. 4-6. The tube component 16 may becomprised of more that one piece of corrugated tubing (FIG. 4), asmaller single piece (FIG. 5) or one single piece of tubing sectionedinto a plurality of ribbed sections, wherein the tubing is adhered tothe inner shaft 12 in more than two locations (FIG. 6).

FIG. 4 shows two pieces of tubing component 16a, 16b. Both pieces areadhered to inner shaft 12 at adhesion points 32. FIG. 5 discloses anembodiment which comprises one smaller piece of tube component 16 whichis adhered to inner shaft 12 at adhesion points 32. FIG. 6 discloses anembodiment which comprises one tube component 16 which has interruptedribbed sections 34 adhered to the inner shaft 12.

FIGS. 7 and 8 illustrate an alternative embodiment in which the tubingcomponent is inflatable to increase the securement pressure on theinside of balloon 14 when the stent is crimped onto the balloon so as tonegated additional recoiling. The full expansion of the tube component16 should only be slightly greater than the diameter of the inside ofthe balloon 14 when the stent 18 is fully crimped onto the balloon 14.

In FIG. 7, the inflating fluid comes through the guide wire lumen 12under pressure from the proximal end or the distal end of the guide wirelumen 12, preferably via a syringe, and fills the tubing component 16through a one-way valve 47 (preferably resisting up to about 4 atm) inthe inner catheter 12.

In FIG. 8, the tubing component 16 is inflated via an additional lumen42 which extends from the proximal end of the catheter along the guidewire lumen 40, much the same as any inflating lumen incorporated toinflate a balloon.

In an alternative embodiment, as shown in FIG. 9, socks or sleeves 51may be incorporated to stretch over the ends of the stent to preventsnagging and to secure the stent onto the balloon. Such sleeves aredemonstrated in U.S. application Ser. Nos. 08/702,149, filed Aug. 23,1996, and 08/701,979, filed Aug. 23, 1996, which are incorporated intheir entirety herein by reference.

In still another embodiment, as shown in FIG. 10, the tubing component16 is slidable axially along the inner shaft 12 and is connected to aretracting wire 50 such that the tubing component may be retracted intothe outer shaft 13 after the balloon has been inflated to reduce theprofile of the balloon 14 when the catheter is removed. The tubingcomponent, since it is not adhered to the inner shaft 12 in thisembodiment, should fit tightly enough on the inner shaft to stay inplace, but not too tightly so that it may be retracted by pulling on theretracting wire 50.

The method of using the stent delivery and deployment assembly 10 ofthis invention, as shown in FIGS. 1 and 2, is described as follows. Theassembly 10 is constructed as described above. Stent 18 is compressed orcrimped onto balloon 14, tube component 16 and the catheter to adelivery diameter D1. This crimping can be done manually or with the aidof tooling specifically designed for the purpose either by the physicianor the manufacturer. In the crimped position, stent 18 closely conformsto the overall profile of balloon 14, tube component 16 and the catheterexcept for the slight slack or looseness due to recoil crimping. Tubecomponent 16 is flexible enough to slightly collapse during crimping andrebound to the extent necessary to compensate for the slack or loosenessdue to recoil crimping, thus securing the stent. As a result, the stentdoes not move out of its position on the catheter during delivery orbecome separated from the catheter within a body vessel. The catheterdistal end is delivered by standard techniques to the deployment sitewithin the body vessel of interest. At this point, stent 18 ispositioned as required by the physician and balloon 14 is fluid inflatedby standard technique to expand stent 18 to its deployment diameter D2.During this expansion, stent 18 is expanded to fill the body vessel.Following deployment of stent 18, balloon 14 is deflated and theassembly is retracted proximally and withdrawn from the body. Ifrequired by the procedure, the site of entry to the body isappropriately closed.

The tube component provided by this invention increases stent securementforce by increasing the frictional force between the tube component, theballoon wall and the internal diameter of the stent in its reducedcrimped delivery diameter. The tube component is more flexible than asolid sheath under the expandable balloon, and thus the entire assemblyhas greater flexibility. This invention has particular advantages forassemblies in which the stent is provided for use as pre-crimped to theballoon and underlying catheter, by increasing the shelf life of thepre-crimped assembly. The tube component also protects the balloonmaterial during crimping by acting as a buffer between the balloonmaterial and whatever may be mounted on the inner shaft, such as markerbands 17. The features and principles described for this invention aresuitable for use with fixed wire, over-the-wire and single operatorexchange assemblies.

Another embodiment of the present invention is shown in FIGS. 11 and 12which illustrate a side profile section showing an inflation expandablestent delivery and deployment assembly generally designated 110.Assembly 110 includes a catheter comprised of inner shafts 112 and 113and an outer shaft 115 of the coaxial type, an inflation expandableballoon 114, an inflation tube component 116 such as an inner balloonand inflation expandable stent 118. Any conventional type of cathetermay be used, such as a catheter of the type generally used for PTA orPTCA angioplasty procedures, for prostate therapy, and TTS endoscopiccatheters for gastrointestinal use. However, coaxial types as shown aremost preferred. The particular catheter 112 shown is formed of abiocompatible and hydrophilic compatible material, such as a lubricouspolyimide or polyethylene. Other suitable materials for the catheter 112include nylons, urethanes, and polypropylene materials compatible withcoatings such as silicone and/or hydrophilic coatings. In addition tohydrophilic compatible materials, any biocompatible material may beused. For example, polyethylene or polypropylene can be coated with ahydrophilic material to render them hydrophilic compatible. suitablecatheters for use according to the present invention include a number ofcatheters available from Scimed Life Systems, Inc., Maple Grove, Minn.,the assignee of the present invention, such as BANDIT™, COBRA™, VIVA™,and VIVA PRIMO™ catheters.

Inflatable tube component 116 is fixed at its distal and proximal end toinner shaft 112 and at its proximal end to inner shaft 113 at a positionto be encompassed within the distal and proximal ends of the outerballoon 114. According to art-recognized convention, the length L-B ofthe balloon 114 is defined as the length of the body portion of theballoon 114, excluding the terminal cone sections 120. As seen in FIG.12, the body portion of the balloon 114 is generally cylindrical when inits deployed or inflated condition. Tube component 116 is illustrated ashaving terminal sections 122 which are more relatively vertical than thecone sections 120 illustrated for the balloon 114. However, it is to beunderstood that, according to the present invention, either of theterminal sections 120, 122 may be relatively cone shaped, relativelyvertical or of any other configuration known to those of skill in thisart. A preferred length L-T of the tube component 116 is illustrated inFIGS. 11 and 12 as substantially equal to the length L-B of balloon 114,and substantially equal to the length L-S of stent 112. However,according to the present invention, stent 112 should be supported by theunderlying tube component 116 for a length sufficient to permitaccomplishment of the stated purpose of the tube component 116, wheninflated, to provide securement pressure for stent 112 to maintain stent112 in position with assembly 110 during delivery. It is also within thepresent invention for tube component 116 to be slightly shorter thanstent 112, for example, the distal end 119 of stent 112 may extenddistally beyond the distal end 121 of tube component 116 (not shown), sothat the distal end 119 of stent 121 can be crimped over the distal end121 of tube component 116 to prevent the distal end 119 of stent 112from catching and tending to further open as it is maneuvered within abody vessel. As has been explained above, tube component 116 is designedand constructed to be inflatable to no more than is necessary tocompensate for recoil crimping of stent 112 and to closely accommodate(or even slightly over-stress) the delivery diameter of stent 112,taking into consideration the thickness of the intervening uninflatedballoon 114. Tube component 116 is inflated through the opening(s) 117of inner shaft 112. Typically, tube component 116 will have a wallthickness of about 0.0002-0.0007 inch and will be inflatable to no morethan about 0.035.-0.045 inches.

Inflating tube component 116 may be formed of either compliant ornon-compliant balloon materials. Compliant materials include lowpressure, relatively soft or flexible polymeric materials, such asthermoplastic polymers, thermoplastic elastomers, polyethylene (highdensity, low density, intermediate density, linear low density), variousco-polymers and blends of polyethylene, ionomers, polyesters,polyurethanes, polycarbonates, polyamides, poly-vinyl chloride,acrylonitrile-butadiene-styrene copolymers, polyether-polyestercopolymers, and polyetherpolyamide copolymers. Suitable materialsinclude a copolymer polyolefin material available from E.I. DuPont deNemours and Co. (Wilmington, Del.), under the trade name Surlyn™ Ionomerand a polyether block amide available under the trade name PEBAX™.Non-compliant materials include relatively rigid of stiff high pressurepolymeric materials, such as thermoplastic polymers and thermosetpolymeric materials, poly(ethylene terephthalate) (commonly referred toas PET), polyimide, thermoplastic polyimide, polyamides, polyesters,polycarbonates, polyphenylene sulfides, polypropylene and rigidpolyurethanes.

A balloon 114 for use according to the present invention may be anyconventional balloon for catheter delivery, such as a balloon of thetype generally used for PTA and PTCA procedures. Typically, balloon 114is fixed at its distal end to inner shaft 112 near the catheter distalend and at its proximal end to outer shaft 115. Balloon 114 is larger indiameter than tube component 116, because balloon 114 must be able toexpand to a larger diameter than tube component 116. Balloon 114 isinflatable through an inflation conduit 123, i.e., the space betweencoaxial inner shaft 113 and outer shaft 115 of the catheter. The distaland proximal ends of balloon 114 are shown in FIGS. 11 and 12 positionedexterior to the distal and proximal ends of tube component 116,respectively, and of a length L-B generally equal to the length L-T ofthe tube component 116. To be compatible with tube component 116illustrated in FIGS. 11 and 12 and described above, balloon 114 isinflatable at deployment to about the diameter of the body vessel inwhich the stent 118 is to be deployed. Balloon 114 may be formed of acompliant or non-compliant material, of the types of compliant materialsdescribed herein above, such as polyethylene or any standard balloonmaterial. Balloon 114 typically has a wall thickness of about0.0007-0.004 inch for example.

A stent for use according to the present invention may be anyconventional type of balloon expandable stent, including stents of thetype used for PTA and PTCA angioplasty procedures, for prostate therapy,and TTS endoscopic catheters for gastrointestinal use. Suitable stentmaterial is biocompatible stainless steel in the form of sheet metal,tube component wire or Nitinol. A preferred stent is described in PCTApplication No. 960 3072 A1, published Feb. 8, 1996, the content ofwhich is incorporated herein by reference. All such stents are wellknown in this art generally and additional examples are described inU.S. Pat. No. 5,507,768 to Lau et al.; in U.S. Pat. No. 5,458,615 toKlemm et al; in U.S. Pat. No. 5,226,889 to Sheiban; in U.S. Pat. No.4,875,480 to Imbert; in U.S. Pat. No. 4,848,343 to Wallsten et al., andin U.S. Pat. No. 4,733,665 to Palmaz. Stent 118 as shown in FIGS. 11 and12 is positioned on balloon 114, the underlying inflatable tubecomponent 116 and the distal end of the catheter. The length L-S ofstent 118 is shown as essentially equal or slightly smaller than thelength L-T of tube component 116 and is positioned on assembly 110 to beco-extensive with tube component 116. In this position, stent 118 isshown in FIG. 11 crimped to its delivery diameter D1, which is about0.035-0.045 inch for example.

As discussed above, despite the most careful and firm crimping of stent118 to closely conform to the overall profile of the catheter unexpandedballoon 114 and underlying inflatable tube component 116, there is acertain amount of "recoil" of stent 118 or a tendency of stent 118 toslightly open from a desired hypothetical minimum crimped diameter. Theactual minimum diameter achievable for fully crimped stent 118 onassembly 110 is referred to as the stent 118 delivery diameter D1. Thistendency of stent 118 to open or recoil slightly when crimped onassembly 110 has been characterized as "recoil crimping". In FIG. 11,inflatable tube component 116 is shown inflated to a diameter which isgenerally sufficient to compensate for any slack or looseness betweencrimped stent 118 and the overall profile of the catheter, theunexpanded balloon 114 and the underlying inflatable tube component 116due to recoil crimping.

FIG. 12 illustrates a side profile section showing a stent delivery anddeployment assembly 110 of this invention with balloon 114 fluidinflated to its fully expanded position. As a result of the fluidinflation of the balloon 114, stent 118 has also been fully expanded toits deployment diameter D2 in which it can be deployed against the wallsof a body vessel in which it is situated.

Tube component 116 may have a shape other than the cylindrical shapedescribed and illustrated with regard to the embodiment shown in FIGS.11 and 12. Further, the tube component may be comprised of more than oneseparately inflatable pouch. For example, as illustrated with regard toFIG. 13, the tube component of an alternative stent delivery anddeployment assembly generally designated 130 can be comprised of threeseparately inflatable pouches 136, 138, 140. The pouches 136, 138, 140are each separately inflatable through their respective inflationconduits 137, 139, 141, and each of the pouches 136, 138, 140 can beinflatable to a different extent. The conduits are formed in the wall ofshaft 132 as can be seen in FIGS. 14-16. The stent delivery anddeployment assembly 130 of FIG. 13 is also comprised of a catheterhaving inner shaft 132 and outer shaft 135, a balloon 134, with itsballoon inflation conduit 139 and the balloon terminal cone sections144, and a stent 142. As has been explained above with reference toFIGS. 11 and 12, stent 142 is crimped to closely conform to the overallprofile of the catheter the unexpanded balloon 134 and the underlyinginflatable pouches 136, 138 140. Even with the most careful and firmcrimping, there is a certain amount of "recoil" of the stent 142 or atendency of stent 142 to slightly open from a desired hypotheticalminimum diameter. In FIG. 13, the first 136 and third 140 pouches areinflated to a slightly larger size than the second pouch 138. Asdiscussed above, the inflation of the pouches 136, 138, 140 to thisconfiguration is generally sufficient to compensate for any slack orlooseness between the crimped stent 142 and the overall profile of thecatheter, the unexpanded balloon 134 and the underlying inflatablepouches 136, 138, 140 due to recoil crimping. Once pouches 136, 138 140have been inflated to the configuration shown in FIG. 13, stent 142 isfirmly secured against axial movement with regard to assembly 130. Thedistal 146 and proximal 148 ends of stent 142 are protected from anypossible unwanted contact with vessel walls during maneuvering, whichhelps to protect the vessel walls from abrasion and also helps toprotect the ends 146, 148 of stent 142 from distortion. Additionally,stent 142 may be of a length such that it fits over pouch 140 and pouch136 as well as over pouch 138.

The method of using the stent delivery and deployment assembly 110 ofthis invention, as shown in FIGS. 11 and 12, is described as follows.The assembly 110 is constructed as described above. Stent 118 iscompressed or crimped onto balloon 114, inflatable tube component 116and the catheter to a delivery diameter D1. This crimping can be donemanually or with the aid of tooling specially designed for the purposeeither by the physician or the manufacturer. In the crimped position,stent we closely conforms to the overall profile of balloon 114,inflatable tube component 116 and the catheter except for the slightslack or looseness due to recoil crimping. Tube component 116 is fluidinflated to the extent necessary to compensate for this slack orlooseness due to recoil crimping. The pressure of force required toinflate tube component 116 to this extent is also referred to assecurement pressure, i.e., the force or pressure needed to secure stent112 in this position. It is to be noted that, since tube component 116is designed and constructed to be capable of fully expanding to no morethan the size necessary to compensate for recoil crimping, there is nopossibility of stent 112 expanding or beginning to open to a largerdiameter. Thus, there is no hazard of stent 112 moving out of itsposition on the catheter during delivery or of becoming separated fromthe catheter within a body vessel. The catheter distal end is deliveredby standard techniques to the deployment site within the body vessel ofinterest. At this point, stent 112 is positioned as required by thephysician and balloon 114 is fluid inflated by standard technique toexpand stent 121 to its deployment diameter D2. During this expansion,stent 112 is expanded to fill the body vessel. Following deployment ofstent 112, balloon 114 and optionally, tube component 116 are deflatedand the assembly 110 is retracted proximally and withdrawn from thebody. If required by the procedure, the site of entry to the body isappropriately closed.

The method of using the stent delivery and deployment assembly 130 ofthis invention, as shown in FIG. 13, is similarly described. Theassembly 130 is constructed as described above. Stent 142 is compressedor crimped to closely conform to the overall profile of balloon 134,inflatable pouches 136, 138, 140 and the catheter except for the slightslack or looseness due to recoil crimping. Pouches 136, 138, 140 areeach fluid inflated to the profile shown in FIG. 13 through separatefluid inflation conduits (not shown) to securement pressure tocompensate for this slack or looseness and to secure stent 142 in thisposition. The overall configuration of pouches 136, 138 140 furtherserves to position stent 142 against axial dislocation during delivery.The catheter is delivered by standard techniques to the deployment sitewithin the body vessel of interest. At this point, stent 142 ispositioned as required by the physician and balloon 134 is fluidinflated by standard technique to expand and deploy stent 142. Followingdeployment of stent 142, balloon 134 and, optionally, pouches 136, 138140 are deflated and the assembly 130 is retracted proximally andwithdrawn form the body. If required by the procedure, the site of entryto the body is appropriately closed.

The inflation tube component provided by this invention also maximizesstent securement force by optimizing the frictional force between theinflating tube component, the balloon wall and the internal diameter ofthe stent in its reduced crimped delivery diameter. The inflation tubecomponent is more flexible than a solid sheath under the expandableballoon, and thus the entire assembly has greater flexibility. Thisinvention has particular advantages for assemblies in which the stent isprovided for use as pre-crimped to the balloon and underlying catheter,by increasing the shelf life of the pre-crimped assembly. The featuresand principles described for this invention are suitable for use withfixed wire, over-the-wire and single operator exchange assemblies.

It should be understood that the various elements and materials of allembodiments could be utilized in each of the other embodiments ifdesired.

The above examples and disclosures are intended to be illustrative andnot exhaustive. These examples and descriptions will suggest manyvariations and alternatives to one of ordinary skill in this art. Allthese alternatives and variations are intended to be included within thescope of the attached claims. Those familiar with the art may recognizeother equivalents to the specific embodiments described herein whichequivalents are also intended to be encompassed by the claims attachedhereto.

What is claimed is as follows:
 1. An assembly for delivery anddeployment of an inflation expandable stent within a vessel,comprising:a catheter having proximal and distal ends and an innershaft; an expandable balloon coaxially mounted on the catheter, theballoon having an expanded state and a collapsed state; and a tubecomponent coaxially mounted on the catheter axially within theexpandable balloon, the tube component having a certain length andforming a continuous covering over the inner shaft along the tube'slength and the tube component having an expanded state, wherein the tubecomponent is capable of being in its expanded state while the balloon isin its collapsed state.
 2. The assembly according to claim 1, the tubecomponent having a plurality of ribs, the assembly further comprising astent, inflation expandable from a delivery diameter to a deploymentdiameter, such that the delivery diameter is reduced from the deploymentdiameter for conforming the stent to the catheter, such that the stent,in its delivery diameter, is coaxially mounted on the catheter near thecatheter distal end, the expandable balloon being capable of expansionof the stent from the delivery diameter to the deployment diameter uponapplication of fluid deployment pressure to the balloon.
 3. The assemblyaccording to claim 2, wherein the tube component is a thermoplasticcorrugated tube adhered to the inner shaft and is formed from a lowmodulus polymer.
 4. The assembly according to claim 3, the tubecomponent being formed from a material chosen from the group consistingof polypropylene, low density polyethylene (LDPE), high densitypolyethylene (HDPE), ethylene vinyl acetate (EVA), nylon, polyester,polyethylene terephthalate ("PET"), Surlyn™, Pebax and urethane.
 5. Theassembly according to claim 3, wherein the diameter of the tubecomponent is approximately equal to the delivery diameter of the stent.6. The assembly according to claim 5, wherein the tube component isessentially equal in length to the stent and wherein the stent ispositioned on the assembly essentially coextensive with the tubecomponent.
 7. The assembly according to claim 2, wherein the tubecomponent is inflatable, such that when the tube component is inflatedit applies radial pressure on the expandable balloon, when the stent isin its delivery diameter.
 8. A method for delivering and deploying astent using an assembly according to claim 2, comprising:providing acatheter having proximal and distal ends, with an expandable ballooncoaxially mounted on the catheter, and a tube component having aplurality of ribs coaxially mounted on the catheter, axially within theexpandable balloon, so that the balloon is in an unexpanded condition;providing a stent which is expandable from a delivery diameter to adeployment diameter; mounting the stent, in a diameter greater than thedelivery diameter, on the balloon; contracting the stent to the deliverydiameter to conform to an overall profile of the catheter, the tubecomponent and the balloon; delivering the assembly to a deployment site;and inflating the balloon to expand the stent to its deploymentdiameter.
 9. The method according to claim 8, wherein the tube componentis a corrugate tubing adhered to the catheter formed of a low moduluspolymer and having a diameter of approximately that of the deliverydiameter.
 10. The method according to claim 8, wherein the tubecomponent is essentially equal in length to the stent and wherein thestent is positioned on the assembly essentially coextensive with thetube component.
 11. An assembly for delivery and deployment of aninflation expandable stent within a vessel, comprising:a catheter havingproximal and distal ends and an inner shaft; an expandable ballooncoaxially mounted on the catheter; a tube component coaxially mounted onthe catheter axially within the expandable balloon, the tube componenthaving a plurality of ribs and wherein the tube component is comprisedof more than one corrugated tube; and a stent, inflation expandable froma delivery diameter to a deployment diameter, such that the deliverydiameter is reduced from the deployment diameter for conforming thestent to the catheter, such that the stent, in its delivery diameter, iscoaxially mounted on the catheter near the catheter distal end, theexpandable balloon being capable of expansion of the stent from thedelivery diameter to the deployment diameter upon application of fluiddeployment pressure to the balloon.
 12. The assembly according to claim6, further comprising marker bands fixed to the inner shaft beneath thetube component.
 13. An assembly for delivery and deployment of aninflation expandable stent within a vessel, comprising:a catheter havingproximal and distal ends and an inner shaft; an expandable ballooncoaxially mounted on the catheter; a tube component coaxially mounted onthe catheter axially within the expandable balloon, the tube componenthaving a plurality of ribs; and a stent, inflation expandable from adelivery diameter to a deployment diameter, such that the deliverydiameter is reduced from the deployment diameter for conforming thestent to the catheter, such that the stent, in its delivery diameter, iscoaxially mounted on the catheter near the catheter distal end, theexpandable balloon being capable of expansion of the stent from thedelivery diameter to the deployment diameter upon application of fluiddeployment pressure to the balloon, the assembly further comprising atleast one sleeve having first and second ends, the first end beingattached to the catheter and the second end covering a portion of thestent, when the stent is in its delivery diameter.
 14. The assemblyaccording to claim 13, comprising two sleeves, one covering each end ofthe stent, when the stent is in its delivery diameter.
 15. An assemblyfor delivery and deployment of an inflation expandable stent within avessel, comprising:a catheter having proximal and distal ends and aninner shaft; an expandable balloon coaxially mounted on the catheter; atube component coaxially mounted on the catheter axially within theexpandable balloon, the tube component having a plurality of ribs; and astent, inflation expandable from a delivery diameter to a deploymentdiameter, such that the delivery diameter is reduced from the deploymentdiameter for conforming the stent to the catheter, such that the stent,in its delivery diameter, is coaxially mounted on the catheter near thecatheter distal end, the expandable balloon being capable of expansionof the stent from the delivery diameter to the deployment diameter uponapplication of fluid deployment pressure to the balloon,wherein the tubecomponent is slidable along the inner shaft and is attached to aretracting means, such that after the stent has been deployed, the usermay slide the tube component proximally along the inner shaft.
 16. Anassembly for delivery and deployment of an inflation expandable stentwithin a vessel, comprising:a catheter having proximal and distal endsand an inner shaft; an expandable balloon coaxially mounted on thecatheter; and a tube component coaxially mounted on the catheter withinthe expandable balloon, wherein the tube component is an expandable tubecomponent coaxially mounted on the catheter, axially within theexpandable balloon, the tube component designed and adapted for fluidexpansion to provide a securement pressure to the stent in the deliverydiameter to maintain the stent in position on the catheter duringdelivery to the deployment site, the assembly further comprising astent, inflation expandable from a delivery diameter to a deploymentdiameter, such that the delivery diameter is reduced from the deploymentdiameter for conforming the stent to the catheter, such that the stent,in its delivery diameter, is coaxially mounted on the catheter near thecatheter distal end.
 17. The assembly according to claim 16, wherein theexpandable tube component is sized and constructed to be fluidexpandable to no more than the delivery diameter and to no more than thesecurement pressure.
 18. The assembly according to claim 16, wherein thetube component is essentially equal in length to the stent and whereinthe stent is positioned on the assembly essentially coextensive with thetube component.
 19. The assembly according to claim 17, wherein the tubecomponent is comprised of more than one inflatable pouch.
 20. Theassembly according to claim 19, wherein the tube component is comprisedof three pouches, with a proximal and distal pouch inflatable to agreater pressure than a medial pouch.
 21. A method for delivering anddeploying a stent using an assembly according to claim 16,comprising:providing a catheter having proximal and distal ends, with anexpandable balloon coaxially mounted on the catheter, and an expandabletube component coaxially mounted on the catheter, axially within theexpandable balloon, so that the balloon and the tube component are eachin an unexpanded condition; providing a stent which is expandable from adelivery diameter to a deployment diameter; mounting the stent, in adiameter greater than the delivery diameter, on the balloon; contractingthe stent to the delivery diameter to conform to an overall profile ofthe catheter, the tube component and the balloon; inflating the tubecomponent to provide to the stent a securement pressure to retain thestent in the delivery diameter; delivering the assembly to a deploymentsite; and inflating the balloon to expand the stent to its deploymentdiameter.
 22. The method according to claim 21, wherein the expandabletube component is sized and constructed to be fluid expandable to nomore than the delivery diameter.
 23. The method according to claim 21,wherein the tube component is essentially equal in length to the stentand wherein the stent is positioned on the assembly essentiallycoextensive with the tube component.
 24. The method according to claim21, wherein the tube component is comprised of more than one inflatablepouch.
 25. The method according to claim 24, wherein the tube componentis comprised of three pouches, with a proximal and distal pouchinflatable to a greater pressure than a medial pouch.
 26. An assemblyfor delivery and deployment of an inflation expandable stent within avessel, comprising:a catheter having proximal and distal ends and aninner shaft; a stent, inflation expandable from a delivery diameter to adeployment diameter, such that the delivery diameter is reduced from thedeployment diameter for conforming the stent to the catheter, such thatthe stent, in its delivery diameter, is coaxially mounted on thecatheter near the catheter distal end; an expandable balloon coaxiallymounted on the catheter axially; and a securement means for securing thestent to the balloon, the securement means coaxially mounted on thecatheter axially within the expandable balloon.
 27. The assembly ofclaim 26 wherein the securement means is an expandable tube component,the component designed and adapted for fluid expansion to provide asecurement pressure to the stent in the delivery diameter to maintainthe stent in position on the catheter during delivery to the deploymentsite.
 28. The assembly of claim 26 wherein the securement means is atube component coaxially mounted on the catheter axially within theexpandable balloon, the tube component having a plurality of ribs.